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All,
Testosterone (T) and other sex hormone levels have always been a topic of interest and concern to CR practitioners. Some men (like me) report dramatically reduced T levels, down to levels not typically seen in any men except the very elderly. Others seem to maintain their T at fairly normal levels for their age.
So which is better?
On the one hand, low testosterone has sometimes been considered a CR "badge of courage" (among men anyway) - indicating one is practicing serious CR, and a positive reflection of the body trading off fecundity for upregulation of maintenance & repair functions (similar to low IGF-1). Women live longer than men across cultures, which some attribute to differences in T level, and eunuchs have been found to live longer, by as much as 15-20 years [2]!
On the other hand, low T often (but not always) has a dramatic effect on libido, and one's overall aggressive drive to succeed / accomplish things. On the health side, negative health outcomes are frequently associated with hypogonadism (low T) in men, including bone health issues [4], sarcopenia [4], cognitive decline [5], and an increased risk of cardiovascular disease.
Regarding the latter, some studies (e.g. see [3] for review) have found T supplementation in hypogonadal men reduces cardiovascular disease risk, but the effect may be limited to obese men with metabolic syndrome, or may result from pharmaceutical industry bias in T supplementation trials [6]. Interestingly, this meta-analysis [6] found that in trials not sponsored by Big Pharma, CVD risk was increased among men receiving supplemental T (OR 2.06, 95% CI 1.34 to 3.17).
So overall, the relationship between the low T that many serious male CR practitioners exhibit and our long-term health & longevity remains an open question. Moreover, hypogonadism in the general population is typically associated with obesity and metabolic syndrome, obviously a very different etiology than hypogonadism in CR practitioners, making the picture even more muddled...
So I reacted with interest, but also some trepidation, when I saw Al Pater post this new study [1] (thanks Al!), on the association of T and other sex hormones with all-cause, cancer and cardiovascular mortality in men. So let's dive in.
First off, this was not a supplementation trial - they measured the natural levels of T, Luteinizing Hormone (LH), Follicle-Stimulating Hormone (FSH), Sex Hormone Binding Globulin (SHBG), free testosterone (FT), and estradiol (E) and in 5300 men of all ages and followed them for an average of 18.5 years to see how many died, from what causes, and how their deaths were associated with these sex hormones.
Here are some interesting statistics at baseline, from the free full text Table 1 (see below):
As expected, T and FT was lower in older men, whereas LH, FSH, and SHBG increased.
Interestingly, smokers had higher T, FT, LH, FSH, E and SHBG than non-smokers at baseline.
Exercise, and particular "competitive sport" participation, was associated with increased T, FT, and lower LH. Could be reverse causality - people with high T are more aggressive and therefore more likely to be attracted to competitive sports...
Overweight and obese men had dramatically lower T and FT at baseline - which will be important later.
Here is the baseline data for sex hormones by demographics for anyone interested in the details (click to enlarge):
Now the interesting part - the mortality results (some of which comes from the text of the supplemental material).
First for cancer mortality:
There was a between-quartile trend towards increased cancer mortality with higher T, but the differences was only really significant in smokers in the highest quartile of T (OR 1.53, 95%CI: 1.14 – 2.08).
In non-smokers, T and FT had virtually no impact on cancer mortality. But there was a pretty strong trend towards more cancer with higher levels of LH and FSH. Keep an eye on LH in particular, it will be important later...
And now, CVD mortality:
Men with total testosterone levels in the highest quartile had a reduced risk of CVD mortality compared to men in the lowest quartile (HR 0.72, 95% CI: 0.53– 0.98). The same relationship held for FT. It is looking bad for us hypogonadal CRers...
But this increased CVD risk with low T (and FT) was in the fully-adjusted model, which included factoring out BMI from the analysis (recall overweight/obese men had dramatically lower T and FT at baseline).
In a model that adjusted for waist circumference instead of BMI, and especially in a model that adjusted for # of markers of metabolic syndrome, the increased risk of CVD with lower T and FT dropped dramatically to the point of no longer being significant between the highest and lowest quintiles of T = (OR 0.66, 95%CI: 0.38-1.16). In other words, to first approximations, if you ignore low T and FT resulting from (or associated with) metabolic syndrome, the association between low T (and FT) and increased CVD goes away...
And now, the all-important All-cause mortality:
There was no significant differences in all-cause mortality across age-standardized quartiles of T (OR 1.01, 95%CI: 0.87-1.18) - to some degree higher cancer risk and lower CVD risk with higher T offset each other, so all-cause mortality was a wash with higher T. The same lack of significant mortality effect was seen for inter-quartile comparison of FT (OR 0.87, 95%CI: 0.75-1.00), but when the trend from lowest to highest quartile of FT was considered, lower FT was associated with increased all-cause mortality (p for trend < 0.02). Again, looking (somewhat) bad for hypogonadal CRers...
An increased all-cause mortality was seen for men in the highest (vs. lowest) quartiles of LH and estradiol, (HR 1.32, 95% CI: 1.14 –1.53) and (HR 1.23, 95% CI: 1.06 –1.43), respectively.
If you are confused by now, perhaps this graphical depiction of the major study findings for all-cause and CVD mortality (with my color highlights) will help (click to enlarge):
As you can see, if we focus on all-cause mortality, higher SHBG, higher LH, and lower FT are associated with increased risk.
So what the heck does all this mean?!?!
Here is my take on it, basically paraphrasing the authors' discussion / speculation. Obesity, and especially metabolic syndrome, are associated with increased mortality risk, and reduced T and FT levels. It may therefore be that low T (& FT) is a marker for impaired androgen signalling in men with metabolic syndrome - i.e. their sex-hormone signalling is messed up, just like some of their other pathways (e.g. insulin signalling) are messed up by all the fat they are carrying. As a result, their LH is elevated - i.e. the "captain" is asking (via increased LH) the "engine room" (i.e. Leydig cells) to produce more T, but the Leydig cells aren't up to the task perhaps because they are gummed up with fat, so T remains low despite elevated LH calling for more. This could be similar in some respects to diabetes, in which insulin doesn't work to clear glucose because of fat so the body calls for the pancreas to produce more, and eventually the beta cells in the pancreas give up the ghost and can't make enough insulin to clear blood glucose.
So what does this mean for CR practitioners?
In us, T is low on purpose from the body's perspective (if I may speak teleologically) - as indicated by our low LH levels (my bloodwork shows my LH to always be near or below the low end of the RR since starting CR). In other words, rather than T being low because the body can't/won't make it (as is the case in guys with metabolic syndrome), our T is low because our body doesn't need or want it.
Again it is perhaps a story similar to IGF-1 and insulin. We (hopefully) have low fasting insulin not because our beta cells are messed up and can't make it (like in late-stage diabetes resulting from metabolic syndrome), but because our bodies don't need/want much insulin - we've got enough insulin to clear the modest amount of glucose we have to process, especially since our insulin sensitivity remains high.
So in short, our low T and low FT may reflect an entirely different, (hopefully) healthier state to be in than having low T and FT as a result of metabolic syndrome.
But then again, that might be just wishful thinking. In particular, our low T and FT may be "intentional" on the part of our body and it may not be good for us in the long run. In other words, our bodies may be hunkering down to survive the (self-induced) famine by lowering T and FT, but in the process sacrificing "non-critical" systems like muscle mass, bone health, and cognitive function - systems that apparently benefit downstream from higher levels of testosterone.
It seems it could go either way. But in any case, we're unlikely to be in as bad shape along these dimensions as men who have low T and FT as a result of metabolic syndrome.
I hope this has done more to clarify than confuse. But re-reading, I'm not so sure...
--Dean
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[1] J Clin Endocrinol Metab. 2015 Oct 21:jc20152460. [Epub ahead of print]
The association of reproductive hormone levels and all-cause, cancer and cardiovascular disease mortality in men.
Agergaard Holmboe S, Vradi E, Kold Jensen T, Linneberg A, Husemoen LL, Scheike T, Skakkebæk NE, Juul A, Andersson AM.
Full Text: http://press.endocrine.org/doi/pdf/10.1210/jc.2015-2460 Abstract CONTEXT: Testosterone levels (T) have been associated with mortality, but controversy exists. OBJECTIVE: To investigate associations between serum levels of total testosterone, SHBG, free testosterone, estradiol, LH and FSH, and subsequent mortality with up to 30 years of follow-up. DESIGN: A prospective cohort study consisting of men participating in four independent population-based surveys (MONICA I-III and Inter99) from 1982 to 2001 and followed until December 2012 with complete registry follow-up. SETTING AND PARTICIPANTS: 5,350 randomly selected men from the general population aged 30, 40, 50, 60 or 70 years at baseline. MAIN OUTCOME MEASURES: All-cause mortality, cardiovascular disease (CVD) mortality and cancer mortality. RESULTS: 1,533 men died during the follow-up period; 428 from CVD and 480 from cancer. Cox proportional hazard models revealed that men in highest LH quartile had an increased all-cause mortality compared to lowest quartile (HR=1.32, 95%CI: 1.14 to 1.53). Likewise, increased quartiles of LH/T and estradiol increased the risk of all-cause mortality (HR=1.23, 95%CI: 1.06 to 1.43, HR=1.23, 95%CI: 1.06 to 1.43). No association to testosterone levels was found. Higher LH levels were associated with increased cancer mortality (HR=1.42, 95%CI: 1.10 to 1.84) independently of smoking status. Lower CVD mortality was seen for men with testosterone in the highest quartile compared to lowest (HR=0.72, 95%CI: 0.53 to 0.98). Furthermore, negative trends were seen for SHBG and free testosterone in relation to CVD mortality, however insignificant. CONCLUSION: The observed positive association of LH and LH/T, but not testosterone, with all-cause mortality suggests that a compensated impaired Leydig cell function may be a risk factor for death by all causes in men. Our findings underpin the clinical importance of including LH measurement in the diagnostic work-up of male patients seeking help for possible androgen insufficiency.
PMID: 26488309
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[2] Curr Biol. 2012 Sep 25;22(18):R792-3. doi: 10.1016/j.cub.2012.06.036.
The lifespan of Korean eunuchs. Min KJ, Lee CK, Park HN.
Free Full Text: http://www.cell.com/current-biology/abstract/S0960-9822(12)00712-9
Abstract
Although many studies have shown that there are trade-offs between longevity and reproduction, whether such trade-offs exist in humans has been a matter of debate [1,2] . In many species, including humans, males live shorter than females, which could be due to the action of male sex hormones. Castration, which removes the source of male sex hormones, prolongs male lifespan in many animals, but this issue has been debated in humans [3] . To examine the effects of castration on longevity, we analyzed the lifespan of historical Korean eunuchs. Korean eunuchs preserved their lineage by adopting castrated boys. We studied the genealogy records of Korean eunuchs and determined the lifespan of 81 eunuchs. The average lifespan of eunuchs was 70.0 ± 1.76 years, which was 14.4–19.1 years longer than the lifespan of non-castrated men of similar socio-economic status. Our study supports the idea that male sex hormones decrease the lifespan of men.
PMID: 23017989
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[3] Expert Opin Drug Saf. 2014 Oct;13(10):1327-51. doi: 10.1517/14740338.2014.950653.
Epub 2014 Aug 19. Cardiovascular risk associated with testosterone-boosting medications: a systematic review and meta-analysis. Corona G(1), Maseroli E, Rastrelli G, Isidori AM, Sforza A, Mannucci E, Maggi M. Author information: (1)Azienda-Usl Bologna, Maggiore-Bellaria Hospital, Medical Department, Endocrinology Unit , Bologna , Italy. INTRODUCTION: Recent reports have significantly halted the enthusiasm regarding androgen-boosting; suggesting that testosterone supplementation (TS) increases cardiovascular (CV) events. AREAS COVERED: In order to overcome some of the limitations of the current evidence, the authors performed an updated systematic review and meta-analysis of all placebo-controlled randomized clinical trials (RCTs) on the effect of TS on CV-related problems. Out of 2747 retrieved articles, 75 were analyzed, including 3016 and 2448 patients in TS and placebo groups, respectively, and a mean duration of 34 weeks. Our analyses, performed on the largest number of studies collected so far, indicate that TS is not related to any increase in CV risk, even when composite or single adverse events were considered. In RCTs performed in subjects with metabolic derangements a protective effect of TS on CV risk was observed. EXPERT OPINION: The present systematic review and meta-analysis does not support a causal role between TS and adverse CV events. Our results are in agreement with a large body of literature from the last 20 years supporting TS of hypogonadal men as a valuable strategy in improving a patient's metabolic profile, reducing body fat and increasing lean muscle mass, which would ultimately reduce the risk of heart disease. PMID: 25139126
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[4] Clin Endocrinol (Oxf). 2005 Sep;63(3):280-93.
Effects of testosterone on body composition, bone metabolism and serum lipid profile in middle-aged men: a meta-analysis. Isidori AM(1), Giannetta E, Greco EA, Gianfrilli D, Bonifacio V, Isidori A, Lenzi A, Fabbri A. Author information: (1)Cattedra di Andrologia, Universita 'La Sapienza', Rome, Italy. andrea.isidori@uniroma1.it OBJECTIVES: Ageing in men is associated with a gradual decline in serum testosterone levels and a concomitant loss of muscle mass, accumulation of central adiposity, impaired mobility and increased risk of bone fractures. Whether androgen treatment might be beneficial in these subjects is still under debate. We have carried out a systematic review of randomized controlled trials (RCTs) evaluating the effects of testosterone (T) administration to middle-aged and ageing men on body composition, muscle strength, bone density, markers of bone metabolism and serum lipid profile. DATA SOURCE: A comprehensive search of all published randomized clinical trials was performed using the MEDLINE, Cochrane Library, EMBASE and Current Contents databases. REVIEW METHODS: Guided by prespecified criteria, software-assisted data abstraction and quality assessed by two independent reviewers, 29 RCTs were found to be eligible. For each investigated variable, we reported the results of pooled estimates of testosterone treatment using the random effect model of meta-analysis. Heterogeneity, reproducibility and consistency of the findings across studies were explored using sensitivity and meta-regression analysis. RESULTS: Overall, 1,083 subjects were evaluated, 625 randomized to T, 427 to placebo and 31 to observation (control group). Weighted mean age was 64.5 years (range 49.9--77.6) and mean serum testosterone was 10.9 nmol/l (range 7.8--19). Testosterone treatment produced: (i) a reduction of 1.6 kg (CI: 2.5--0.6) of total body fat, corresponding to -6.2% (CI: 9.2--3.3) variation of initial body fat, (ii) an increase in fat free mass of 1.6 kg (CI: 0.6--2.6), corresponding to +2.7% (CI: 1.1--4.4) increase over baseline and (iii) no change in body weight. The effects of T on muscle strength were heterogeneous, showing a tendency towards improvement only at the leg/knee extension and handgrip of the dominant arm (pooled effect size=0.3 standard mean difference (SMD), CI: -0.0 to 0.6). Testosterone improved bone mineral density (BMD) at the lumbar spine by +3.7% (CI: 1.0--6.4%) compared to placebo, but not at the femoral neck, and produced a consistent reduction in bone resorption markers (pooled effect size = -0.6 SMD, CI: -1.0 to -0.2). Testosterone also reduced total cholesterol by 0.23 mmol/l (CI: -0.37 to -0.10), especially in men with lower baseline T concentrations, with no change in low density lipoprotein (LDL)-cholesterol. A significant reduction of high density lipoprotein (HDL)-cholesterol was found only in studies with higher mean T-values at baseline (-0.085 mmol/l, CI: -0.017 to -0.003). Sensitivity and meta-regression analysis revealed that the dose/type of T used, in particular the possibility of aromatization, explained the heterogeneity in findings observed on bone density and HDL-cholesterol among studies. CONCLUSION: The present analysis provides an estimate of the average treatment effects of testosterone therapy in middle-aged men. Our findings are sufficiently strong to justify further interventional studies focused on alternative targets of androgenic treatment carrying more stringent clinical implications, in particular the cardiovascular, metabolic and neurological systems. PMID: 16117815
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[5] Mol Neurobiol. 2015 Jul 8. [Epub ahead of print]
Low Testosterone Level and Risk of Alzheimer's Disease in the Elderly Men: a Systematic Review and Meta-Analysis. Lv W(1), Du N(1), Liu Y(1), Fan X(1), Wang Y(1), Jia X(2), Hou X(3), Wang B(4). Sex steroids can positively affect the brain function, and low levels of sex steroids may be associated with worse cognitive function in the elderly men. However, previous studies reported contrary findings on the relationship between testosterone level and risk of Alzheimer's disease in the elderly men. The objective of this study was to comprehensively assess the relationship between low testosterone level and Alzheimer's disease risk in the elderly men using a meta-analysis. Only prospective cohort studies assessing the influence of low testosterone level on Alzheimer's disease risk in elderly men were considered eligible. Relative risks (RRs) with 95 % confidence intervals (95 % CI) were pooled to assess the risk of Alzheimer's disease in elderly men with low testosterone level. Seven prospective cohort studies with a total of 5251 elderly men and 240 cases of Alzheimer's disease were included into the meta-analysis. There was moderate degree of heterogeneity among those included studies (I (2) = 47.2 %). Meta-analysis using random effect model showed that low plasma testosterone level was significantly associated with an increased risk of Alzheimer's disease in elderly men (random RR = 1.48, 95 % CI 1.12-1.96, P = 0.006). Sensitivity analysis by omitting one study by turns showed that there was no obvious change in the pooled risk estimates, and all pooled RRs were statistically significant. This meta-analysis supports that low plasma testosterone level is significantly associated with increased risk of Alzheimer's disease in the elderly men. Low testosterone level is a risk factor of worse cognitive function in the elderly men. PMID: 26154489
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[6] BMC Med. 2013 Apr 18;11:108. doi: 10.1186/1741-7015-11-108.
Testosterone therapy and cardiovascular events among men: a systematic review and meta-analysis of placebo-controlled randomized trials. Xu L(1), Freeman G, Cowling BJ, Schooling CM. Author information: (1)School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, 21 Sassoon Road, Pokfulam, Hong Kong, China. Comment in Evid Based Med. 2014 Feb;19(1):32-3. BACKGROUND: Testosterone therapy is increasingly promoted. No randomized placebo-controlled trial has been implemented to assess the effect of testosterone therapy on cardiovascular events, although very high levels of androgens are thought to promote cardiovascular disease. METHODS: A systematic review and meta-analysis was conducted of placebo-controlled randomized trials of testosterone therapy among men lasting 12+ weeks reporting cardiovascular-related events. We searched PubMed through the end of 2012 using "("testosterone" or "androgen") and trial and ("random*")" with the selection limited to studies of men in English, supplemented by a bibliographic search of the World Health Organization trial registry. Two reviewers independently searched, selected and assessed study quality with differences resolved by consensus. Two statisticians independently abstracted and analyzed data, using random or fixed effects models, as appropriate, with inverse variance weighting.
RESULTS: Of 1,882 studies identified 27 trials were eligible including 2,994, mainly older, men who experienced 180 cardiovascular-related events. Testosterone therapy increased the risk of a cardiovascular-related event (odds ratio (OR) 1.54, 95% confidence interval (CI) 1.09 to 2.18). The effect of testosterone therapy varied with source of funding (P-value for interaction 0.03), but not with baseline testosterone level (P-value for interaction 0.70). In trials not funded by the pharmaceutical industry the risk of a cardiovascular-related event on testosterone therapy was greater (OR 2.06, 95% CI 1.34 to 3.17) than in pharmaceutical industry funded trials (OR 0.89, 95% CI 0.50 to 1.60). CONCLUSIONS: The effects of testosterone on cardiovascular-related events varied with source of funding. Nevertheless, overall and particularly in trials not funded by the pharmaceutical industry, exogenous testosterone increased the risk of cardiovascular-related events, with corresponding implications for the use of testosterone therapy. PMID: 23597181